Example embodiments relate to an analog-to-digital converter (ADC), and more particularly, to an ADC for controlling a gain, an image sensor including the ADC to control sensitivity, and a method of operation of the analog-to-digital converter.
Photosensitivity control is relatively important function in digital image pick-up devices. Photosensitivity cannot be changed when images are photographed using a film, unless the film is changed, but the photosensitivity can be controlled with relative ease by operating a machine in digital image pick-up devices.
Generally, sensitivity control is relatively important function of image sensors. The sensitivity control is usually carried out by controlling the gain of an ADC included in an image sensor. A variable gain amplifier (VGA) is additionally provided before an input unit of the ADC to control the gain, so that the sensitivity of the image sensor is controlled. The ADC including the VGA is not efficient because it requires additional power and area, and may not provide high gain. Therefore, an ADC for controlling the sensitivity of an image sensor by varying a gain of the ADC without an additional element is desired.